Map Projections in ArcGIS Pro

hi so this video is going to outline how projections work in arcgis pro if there's one thing that students tend to get confused on it has to do with map projections and how they work in the GIS software so hopefully this video will will help us help us out with that and i'm just going to run through some examples with some simple shape files and hopefully after watching this you'll understand a little bit better how the projections work in the software so to get started i'm going to open up our GIS pro and I'm just gonna start a a blank map here [Music] okay and so I'm gonna see excuse me here and go to insert I'm going to insert a new map and it's a lot of you know the topo map is the default backdrop that ArcGIS Pro puts in the background I always like to change that so I'm just gonna go to base map and load in the the hybrid imagery okay so I guess the first thing to point out in terms of projections is if we if i zoom out here and we can see the whole world imagery we can see that it's in the shape of a square okay so it's a flat map here in the software what I like to ask my students is what projection can you tell just by looking at this what projection maybe the data is in and the answer would be it's in a cylindrical projection and you can tell that this is a Mercator map actually you can tell that because look at how big Antarctica is look at how huge Greenland is obviously we know by now that Greenland is not that big and the reason it's showing up that big and the reason Antarctica is showing up that big here on the map is because this is a cylindrical projection and the farther away you get from the equator the more stretched out things become on the map but the first thing to point out in terms of projections in the software is that arcgis pro takes on the properties of the very first piece of data you add into the map okay so for example we added in this world imagery along with the hybrid reference layer into our map first and now if we check the projection of this world imagery so for example if i highlight world imagery then i right-click on it and go to properties and I go to source and I go to spatial reference we can see that the projection this piece of data is in is a wgs84 web Mercator auxilary sphere ok so that's that's what this data is projected in similarly if we click on our project in this case it's just called map if we click on the map in other words if I right-click on this and go to properties and go to coordinate system notice it's exactly the same and that is because the first piece of data we added into ArcGIS pros the world imagery it has this projection therefore our map has the same projection now the good thing about arcgis pro is it has something called project on the fly ok what that means is if i right-click on my map properties and let's say i don't want to use this web Mercator auxilary sphere projection since we're going to be making a map of Wyoming and I want to use UTM nad83 zone 13 ok so if I right click map and go to properties and go to a coordinate system and remember from lecture and from other labs we have done UTM is a projected coordinate system ok so if I hit the arrow next to projected scroll down to UTM the datum I want to use is nad 83 and then Casper Wyoming is in zone 13 North highlight that and click OK okay now my map if I right-click on map again and go to properties this is what projection it's in UTM nad83 zone 13 North did I do anything to the projection of the world imagery now I did if I right-click on the world imagery and check its projection it is still in wgs84 web Mercator auxilary sphere okay so the reason so art ArcGIS Pro is something called Project on-the-fly you can have as many data layers and your contents paid as you want and arcmap will do the mathematical calculations behind the scene and make it match up to whatever projection is in your map in this case UTM zone 13 north okay let's add in another piece of data just to kind of show you that point so I'm going to hit the add data button and I'm gonna go to my I'm gonna go to my desktop and I'm gonna go to my projections lab data and I'm going to add in the state's shapefile okay it's lining up just fine it looks like it looks like the states are lining up right where they should be [Music] let's check the projection of that state shapefile again right click States go to properties go to spatial reference and this particular file is in GCS North American nineteen eighty-three again it's different from UTM so we have the world imagery in wgs84 web auxilary sphere we have the states in GCS north american eighty-three but again remember my map is still in UTM nad83 zone 13 north so just to hit the point home again you can put your map in any projection you want and because the software has project on the fly it will make all of these other layers that you have in your map lineup ok so the thing to remember here is arduous pros project on the fly you can have your software or your map being any projection you want and as long as these other files have a projection it will it will make them it will usually make them line up ok ok let's let's look at another instance or example with projections so let's I'm going to go ahead and add in another shape file to my map and I'm gonna add the cities in ok so I've added my cities in I'm going to make the symbol something a little bigger than I can see I'll just make them a red-dot just so we can see it better notice what's happening here my my shape file loaded in just fine but you can tell they certainly aren't lined up where they should be they are clearly they're out in the Pacific Ocean and clearly south of the United States ok so if I ever run into a piece of data that that doesn't look like it's lining up the way it should the first thing I do is check its projection all right so I'm going to right-click on cities and go to properties I'm going to go to spatial reference up and look and see what we have here this is unknown coordinate system in other words this shapefile does not have a map projection when something doesn't have a map projection arcgis pro does not know what to do with it basically what it'll do is it'll put it in the middle of the map but it has no clue as to where this piece of data should go okay and so let me should let me show you how to fix this the thing you have to do is you have to give it a projection and you can't just give it whatever projection you want you have to if someone sends you a piece of data that doesn't have a projection you have to call that person and ask them hey what projection did you create this file if you got it off a website and it doesn't have a projection you need to go into that website and figure out hopefully on the website it'll tell you what projection the data should be if you've got some GPS data from someone and it's not lining up correctly you need to call that person and ask them hey what what kind of map projection did you use on your GPS you can't just give it whatever projection one it has to be what it was created okay now in this particular example I'm going to tell you right now just because I know and I've worked with this file before that this particular shapefile should be in North a Lambert conformal conic okay so now that we know what projection it should be in because I told you North America Lambert conformal conic if if a shape file or a piece of spatial data does not have a projection you use a tool called define projection okay so in the tool box you're going to use a tool called define projection to fix this so we're going to go up here to analysis we are going to click on tools and then over here in the in the search box we are going to type in define projection and here it is right here the first one that popped up define projection so I'm going to click on that okay so our input data set is going to be cities now we need to tell it what coordinate system we want it to be in so we're gonna select we're going to click the button over here to the right it says select coordinate system North America Lambert conformal conic is a projected coordinate system so I'm going to hit the arrow next to projected I'm going to go to continental North America I'm going to find North America Lambert conformal conic and there it is right there again the way you know that this is the correct projection is just because I've worked with this data before and I'm telling you what it is again if you ever get a piece of spatial data that does not have a projection you have to find out from whoever made that piece of data what projection it should be and then you use this tool to put it in that correct projection again in this case it's North America Lambert conformal conic I'm going to highlight it click OK and then I'm going to run the tool now watch what happens to the cities file see at it it moved it the tool ran and it moved it where it should go okay that's exactly what should happen well if i zoom in a little bit yep Cheyenne is where it should be I'm assuming this is Fort Collins you have four columns looks like it's where it should be I can check a few other cities Fargo looks like it's all all lining up where it should be so looks like we're good so just to again a couple things to remember with the ArcGIS Pro software you can have the projection of your overall map and the way you check that is you right-click on map go to properties and as you can see for example mine is an nad83 UTM zone 13 you can have individual projections for your pieces of data and the way you find that out is right click on the data and go to properties go to spatial extent and we just fixed this one it used to say unknown now it's in North America Lambert conformal conic okay the states is in GCS North American 83 the world imagery is in wgs84 web Mercator auxilary sphere okay remember the reason all three of these files have our different projections but the reason they are lining up with our UTM projection that we have in our map is because our geo Sparrow has project on the fly and that what that means again is the software can do the mathematical calculations for these three files and change their projection on the fly to match that of our map okay so we're not we're not changing the section of these files were just sort of doing it behind the scenes and on the fly so that everything lines up so I hope that makes sense hopefully that will help you with the exercise you have to do as always email call or text with any questions

Channel: Jeff Sun

Views: 5,183

Rating: 5 out of 5

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Id: 2MKyts2e0Ww

Length: 15min 43sec (943 seconds)

Published: Wed Feb 06 2019